The present invention is directed to a clinch nut and apparatus for installing this clinch nut to a workpiece. More particularly, the present invention is directed to a sheet metal clinch nut which can be easily and economically manufactured and installed.
Several attempts have been made to devise a clinch nut with space to receive a workpiece extrusion so that the nut may be staked into position on a workpiece. These prior clinch nuts are made from rod stock and necessarily involve expensive manufacturing steps of boring, counterboring and thread tapping in addition to the difficulties in handling and machining such parts. Further, each of these clinch nuts relies on an undercut to receive extruded material to retain the nut to the workpiece. Such undercuts are difficult to machine and unreliable in their retention characteristics due to the reluctance of the extruded metal to fill the undercut.
The present invention overcomes the difficulties and deficiencies of these prior art clinch nuts. The clinch nut in one form of the present invention comprises first and second arms which are interconnected. The first and second arms are stamped from sheet material and each arm includes an aperture which can be formed during the stamping step or easily added or modified during a secondary machining step. The clinch nut is bent into a U-shaped configuration to bring the two apertures into axial alignment with the interconnecting portion forming the base of the U. One aperture is larger than the other so as to accommodate an extruded portion of the workpiece. The other aperture is sized to accommodate a self-tapping screw shank which initially taps into the extruded metal and then into the aperture in the second arm. As the screw is tightened into the clinch nut, it will draw the second arm angularly towards the first as a result of the resilience of the spring arm formed by the interconnecting portion at the base of the U. This will effectively cause a locking of the threads and prevent backing out of the fastener. In addition, whereas most clinch nuts must be made for a particular workpiece thickness, the clinch nut of the present invention can accommodate a range of material thicknesses since the area between the two arms can accommodate the additional extruded material.
In other forms of the present invention the nut has a tubular body with an entering portion of relative large diameter for receipt of the extruded portion of the workpiece, and an extended portion of lesser diameter for threaded association with a screw. The larger diameter portion is axially collapsed upon itself to surround and grip a part of the workpiece extrusion.
The clinch nut of the present invention is capable of improved retention by the workpiece, can be more easily and cheaply made of sheet metal, and can provide a locking feature not available with prior art clinch nuts. These and other features, advantages and objects of the present invention will be more fully appreciated following a reading of the following description when taken in conjunction with the accompanying drawings.